Flow rate of polygonal grains through a bottleneck: Interplay between shape and size

TL;DR

This study uses two-dimensional simulations to analyze how polygonal and circular grains pass through a silo bottleneck, revealing that shape and size criteria significantly influence flow rates and packing behavior.

Contribution

It demonstrates the complex interplay between particle shape, size, and flow rate, highlighting the importance of size definition criteria in granular flow simulations.

Findings

Polygonal grains have lower flow rates than disks.

Packing fraction and exit velocity are reduced for polygons.

Flow rate varies with shape and size criteria.

Abstract

We report two-dimensional simulations of circular and polygonal grains passing through an aperture at the bottom of a silo. The mass flow rate for regular polygons is lower than for disks as observed by other authors. We show that both the exit velocity of the grains and the packing fraction are lower for polygons, which leads to the reduced flow rate. We point out the importance of the criteria used to define when two objects of different shape are considered to be of the same size. Depending on this criteria, the mass flow rate may vary significantly for some polygons. Moreover, the particle flow rate is non-trivially related to a combination of mass flow rate, particle shape and particle size. For some polygons, the particle flow rate may be lower or higher than that of the corresponding disks depending on the size comparison criteria.